1. Technical Field
The present invention relates to a light source device and a projector.
2. Related Art
In recent years, while demands for downsizing of projectors are growing, in accordance with increase in output power of semiconductor lasers and appearance of blue semiconductor lasers, projectors using laser sources have been developed. The projectors of this kind are capable of having a sufficiently large color reproduction range because the wavelength band of the light source is narrow, and also capable of downsizing and reducing the number of components, and consequently, have a great potential as display devices of the next generation.
However, in the projectors using the laser sources, there are some cases in which a phenomenon so called “scintillation (or “speckle”)” is caused, when performing display with image light. In the scintillation, interference of light is caused on scatterer such as a screen, which distributes bright points and dark points in a stripe manner or a variegated manner.
The scintillation causes the observer to have a dazzling feeling, and becomes a cause of exerting an adverse influence on the observer such as an uncomfortable feeling when appreciating images. In particular, the laser beams, which are light beams with high coherence, are apt to cause the scintillation. However, in recent years, even the lamp light sources have been getting higher coherency with shorter arc, and therefore, technologies for removing the scintillation have been getting important, and technologies for reducing the speckle noise have been proposed (see, e.g., JP-A-6-20809 (hereinafter referred to as Document 1) and JP-A-2007-33576 (hereinafter referred to as Document 2)).
In the display described in the Document 1, red laser beam, green laser beam, and blue laser beam are composed, and transmitted through a diffusion element rotated. On this occasion, reduction of the speckle noise can be achieved by rotating the diffusion element at a sufficiently high speed.
Further, the illumination device described in the Document 2 is provided with a light source device for emitting a light beam and a diffracting optical element for equalizing the illumination distribution of the incident light. Thus, the diffracting optical element executes rectangular conversion on the light emitted from the light source device to illuminating a predetermined illumination area. In a projecting image display device using this illumination device, a light valve is disposed so as to be opposed to the diffracting optical element to irradiate the light valve with the diffracted light generated by the diffracting optical element.
In the related art described above, there remains the following problem unsolved.
Specifically, in the display described in the Document 1, since the diffusion plate diffuses the light, efficiency of the light problematically drops.
Further, in the illumination device described in the Document 2, although the diffracting optical element generates the illumination light for illuminating the predetermined illumination area, there are some cases in which high-frequency noise is caused in the illumination light generated by the diffracting optical element. In such cases, it is difficult for the diffracting optical element to generate the illumination light with an even intensity distribution.